Working up of distillation fractions containing alcohols and hydrocarbons



United States Patent WORKING UP OF DISTILLATION FRACTIONS CONTAININGALCOHOLS AND HYDRO- CARBONS Karl Biichner, Duisburg-Hamborn, andHeinrich Schwarz,

Oberhausen-Sterkrade, Germany, assignors to RuhrchemieAktiengesellschaft, ()berhausen-Holten, Germany, a corporation ofGermany No Drawing. Application March 31, 1954 Serial No. 420,184

'Claims priority, application Germany April 15, 1953 7 Claims. (Cl.260-413) This invention relates to improvements in the working up ofdistillation fractions containing alcohols and hydrocarbons.

Higher alcohols may be produced by catalytically adding carbon monoxideand hydrogen to mixtures of olefins, such as isomeric and/ or homologuemixtures. The catalytic addition may be effected in the absence orpresence of saturated hydrocarbons. As a result of the catalyticaddition, the next higher alcohols are produced. The olefins in themixture may be isomeric with respect to the position of the double bondand/ or if alkyl side chains are present, with respect to these sidechains. The alcohol mixtures obtained in this manner must be separatedby distillation for further commercial use. This may result in fractionsin which branch-chained alcohols and hydrocarbons distil over in thesame boiling range, and for this reason cannot be separated bydistillation. These fractions, which hereinafter will be referred to inboth the specification and claims as intermediate fractions could not beutilized in an advantageous manner up to the present.

The intermediate fractions obtained could be charged to a subsequentdistillation. This, however, would merely result in a continuousincrease of the intermediate frac tion. Prior to the present invention,these intermediate fractions could neither be utilized as hydrocarbonproducts due to their high content of alcohols and could not be utilizedas alcohol products due to their high hydrocarbon content.

In addition to these alcohol hydrocarbon distillation fractions obtainedin the processing of raw alcohols obtained from olefins of theFischer-Tropsch synthesis, other similar hydrocarbon alcohol-containingfractions are obtained from other starting materials. A similar type ofintermediate fraction is obtained from the fractionation of crudealcohols obtained from olefins which have been formed by thechlorination and dechlorination of parafiins. In the treatment ofpolymerized olefins produced from liquid or gaseous unsaturatedpetroleum hydrocarbons, similar fractions may also be obtained.

One object of this invention is a process for working up suchintermediate fractions which contain alcohols and hydrocarbons toproduce branch-chain fatty acids. This, and still further objects willbecome apparent from the following description:

It has now been found that fractions containing alcohols andhydrocarbons, such as the intermediate fractions described above, may beprocessed in an advantageous manner with the formation of valuablebranch-chain fatty acid by the treatment of such a fraction with causticalkali in amount substantially corresponding to the hydroxyl number ofthe intermediate fraction or slightly in excess thereof at temperaturesof 250350 C. at increased pressure; thereafter distilling ofi thehydrocarbons present at any desired pressure, injecting water into theagitated melt under increased pressure, removing the water-containingpasty soaps thus formed at a temperature not in excess of 200 C. fromthe reaction vessel, and decomposing these soaps in the known mannerwith mineral acids after dissolution in water with the addition, ifdesired, of watersoluble alcohols and after extraction withWater-insoluble salts.

The boiling range of the aforementioned intermediate fractions at normalatmospheric pressure (760 mm. Hg) is approximately as follows, dependingon the molecular size: v

o c. 0 205445 0 j 240-275 c 260-290 (3 280-305 6 s 295-320 For carbonmonoxide hydrogenation products produced by means of iron catalysts andwith a production of 5,500 kilograms of alcohol, there are obtainedapproximately 1,000 kilograms of intermediate fractions to be processedin accordance with the invention and 15,000 kilograms of first runningswhich substantially consist of paraffinic hydrocarbons.

The branched-chain fatty acids obtainable in this manner are suited forvarious commercial uses. They may, for example, be processed to give lowpour point ester oils. It is also possible to obtain textile auxiliaryagents, cold-resistant plasticizers, and mineral-oil additivestherefrom. The process of the invention thus makes possible theeconomical conversion into valuable finished products of intermediatefractions which have hitherto been treated as waste products.

The process is preferably carried out in such a manner as to subject theintermediate fractions to be processed to a treatment with alkali at250-350 C. and superatmospheric pressure and thereafter to effect thethen possible separation by distillation into hydrocarbons andoxygenated products.

The treatment with caustic alkali should be effected with an amount ofalkali corresponding to the hydroxyl numberofthe mixture'treated. Theamount of caustic alkali should preferably not be in excess of of thetheoretically required quantity based on this hydroxyl number. Besidessodium hydroxide, the alkali treatment may also be effected withpotassium hydroxide. Based on the hydroxyl number present, quantities ofalkali which, if desired, are far in excess of 10% of thestoichiometrically required quantity maybe used in this case. Foreconomic reasons, however, not more caustic alkali is used than isrequired for the conversion of the alcohols into carboxylic salts. Thequantity which should preferably be used is generally about 110% of thetheoretically required quantity. The alkali treatment may be effected atatmospheric pressure of more than 10 kg. per square centimeter andpreferably more than 50 kg; per square centimeter. The gas pressuresdeveloping during the alkali treatment are dependent on the volatilityof the hydrocarbons involved. If highly branched carboxylic acids having12' and more carbon atoms in the molecule are produced, thenthe gaspressures will rise not higher than to 10-100 kg. per square centimeter,

The hydrogen split off during the alkali treatment should preferably becontinuously removed, so that the pressure formed does not exceed morethan 50 kg. per sq. cm. The hydrogen split off is thus preferablycontinuously removed at pressures in excess of 50 kg. per squarecentimeter. After the termination of the hydrogen evolution, thepressure is released and preferably released to atmospheric pressure,while substantially maintaining the melting temperature. This will causethe hydrocarbons to distil off. In the case of hydrocarbons having amolecular size of more than C reduced pressure may be required for thedistillation. In any case, as soon as the distillation of thehydrocarbons ceases, it is preferable to continue the distillation byreducing the pressure and maintaining the melting temperature, so thatpractically all the hydrocarbons can be re moved, thus eliminating thenecessity of a later extraction of the soap solution for the purpose ofremoving the unsaponifiable portions.

After the removal of the hydrocarbons by distillation, water is injectedinto the reaction vessel preferably with stirring. The amount of waterinjected may be between and 50%, preferably 30% of the melt treated. Thepaste formed after the injection of the water is removed from thereaction vessel at temperatures not in excess of 200 C. The removal fromthe reaction vessel, as, for example, the pressure vessel, is effectedby forcing the paste from the vessel by an internally applied pressureor externally applied partial vacuum. The soap paste, while stirring, isallowed to flow into a quantity of water which is preferably 2. to 4times that of the soap paste.

1 The process may, for example, be carried out as folows:

The mixture required of alkali and intermediate fraction is placed intoa pressure-resistant melting vessel which is suitably lined with copper.The pressure vessel is then closed, purged with nitrogen, and heatedwhile constantly stirring with the initial nitrogen pressure being 1 to2 kg. per square centimeter. Depending upon the partial pressure of thehydrocarbons present, the reaction pressure increases and isadditionally increased by the splitting-0E of hydrogen commencing atabout 250 C. After a pressure of about 50 kg. per square centimeter isreached, sufficient hydrogen is allowed to blow off through a pressurerelief valve as to maintain said pressure of 50 kg. per squarecentimeter.

The reaction is now allowed to proceed to completion, while increasingthe temperature to about 320 C. and thereafter the hydrogen is removedby completely releasing the pressure. Depending upon the boiling rangeof the hydrocarbons subjected to the treatment with alkali, theprevailing pressure will be sufficient to cause a distillation of thehydrocarbons. With hydrocarbons of the molecular size C a distillationof this kind will take place under a pressure of as low as about 6 kg.per square centimeter. As soon as this distillation of hydrocarbonsceases, the distillation is continued by reducing the pressure whilemaintaining the melting temperature. In this manner, practically all ofthe hydrocarbons can be removed from the soap, thereby eliminating thenecessity of a later extraction of the soap solution for the purpose ofremoving unsaponifiable portions, as is required for the production ofcommercially pure fatty acid products.

After the complete removal of the hydrocarbons, water is injected intothe pressure vessel, while the stirring is continued, and while the meltis still in the hot liquid state. Prior to that, the hydrogen formed isadvantageously completely removed. In this case, approximatelyatmospheric pressures may be used in introducing the water. If the wateris to be injected tothe melt prior to the complete removal of thehydrogen, a pressure must be used which is in excess of theprevailinghydrogen pressure. In this case, the pressures to be usedrange up to 50 kg. per square centimeter. The reaction vessel in thiscase must be sufiiciently resistant to the increase in pressure takingplace by the partial pressure of water vapor. The temperature of themelt ranges at about 200-250 C. The water to be injected may be attemperatures of approximately l0-80 C. Less than 50% of water, based onthe weight of the melt, will generally be injected. Larger quantitiesmay be used if the capacity of the reaction vessel is large enough. Bythe injection of water, the anhydrous soap, which is very hard aftersolidification, is converted into a soft-water-conraining pasty mass.This paste is particularly well suited for processing because the soapmaterial in this state can be forced or pumped out of the reactionvessel at temperatures not in excess of 200 C. Moreover, the dissolutionof this soap paste in water required for precipitating the branchedfatty acids by means of acids can be effected in the pasty state withoutany difiiculty, while the dissolution of an anhydrous soap, even afterthorough comminution, requires a long time.

The decomposition of the resulting soap by mineral acids for the purposeof recovering free fatty acids is effected by known processes. The fattyacids may completely be set free by mineral acids. It is possible,however, if desired, to separate at first an acid soap by means ofcarbon dioxide, thereby saving a part of the mineral acid required. Thedecomposition of the soaps obtained by the alkali treatment may, forexample, be effected with sulfuric, hydrochloric, nitric, carbonic,formic, acetic or oxalic acids. The mineral acids are preferably used inthe form of 10-20% solutions. If carbon dioxide is to be used, thepressure applied must be not less than 1-2 kg./ square centimeter. Thedecomposition of the soaps may be effected at normal room temperature orat temperatures of as high as about C. In any case, the reaction mixturemust thoroughly be stirred in decomposing the soaps.

The branched fatty acid obtained by the process of the invention can befreed from coloring matter by distillation. To obtain chemically pure.fatty acids, the aqueous soap solution may, of water-soluble alcohols,be treated with hydrocarbons, thereby removing small portions ofunsaponifiable constituents still present. If desired, a fractionalseparation by molecular sizes may be obtained by using suitableextracting agents (see German Patent No. 868,951). Moreover, it ispossible, by partial precipitation by means-of mineral acids, to removesmall amounts of straight-chain fatty acids which are present in themixture of branchchain fatty acids obtained in accordance with theinvention. This is achieved with an incomplete saponification which, ifnecessary or desired, is repeated several times with the quantities ofalkali used being kept sufficiently low that no noteworthy separation bymolecular sizes occurs.

The process of the invention is particularly advantageous for theprocessing of raw alcohols obtained from olefins of the Fischer-Tropschsynthesis. It is, however, also applicable to alcohol mixtures obtainedfrom other starting materials. It is, in addition, well suited for thetreatment of intermediate fractions of crude alcohols obtained fromolefins, which, in turn, are formed by chlorination anddehydrochlorination of paraffins. Crude alcohol mixtures frompolymerized olefins produced from liquid or gaseous unsaturatedpetroleum hydrocarbons may also be processed in accordance with theinvention.

The water-soluble alcohols used may be low-cost low molecular weightalcohols, e. g. commercial methyl alcohol (methanol), denatured ethylalcohol or isopropyl alcohol. Suitable solvents are saturated aromaticand hydroaromatic hydrocarbons boiling between 50 and 250 C.

Further details will become apparent from the following examples, whichare given by way of illustration and not limitation:

if desired after admixture Example 1 Density at 20 C 0.801 Refractiveindex, n 1.4391

Neutralization number 0.4 Saponification number 4.6 Hydroxyl number 110Iodine number 2 Carbonyl number 3 Pour point C -4 To this product therewere added 52.2 grams caustic soda (NaOH), corresponding to 110% of thehydroxyl number of the mixture. Thereafter, the pressure vessel wasclosed, purged two times with nitrogen, and then a nitrogen at apressure of 2 kg. per square centimeter was passed into the gas space ofthe pressure vessel. Following this, the stirrer was started and thepressure vessel was heated. At 320' C. a pressure of 50 kg. per squarecentimeter was reached. This pressure was not allowed to increase beyond50 kg. per square centimeter by opening a needle valve on the vessel. Inthis manner, 11 normal liters of hydrogen were removed from the pressurevessel. When, at 320 C. the pressure no longer increased, all of thehydrogen was withdrawn, while maintaining the temperature. The hydrogenwithdrawn, after being released from pressure, corresponded to a gasquantity of 55 normal liters.

At a reaction pressure of as low as 6 kg. per square centimeter,hydrocarbons distilled from the pressure vessel, and were condensed by acooler and separated from the gaseous products. After atmosphericpressure was reached, a vacuum of about mm. Hg was applied, whereby theremainder of the hydrocarbons distilled 01f from the reaction productcontained in the pressure vessel. This resulted in 308 grams oilyconstituents corresponding to 51.4% of the material charged. Based onthe characteristics given above, a content of neutral oil of 52% wastheoretically to be expected.

150 cc. of water were then injected by means of nitrogen into thepressure vessel, which had meanwhile cooled to 250 C., while continuingthe stirring for about 10 minutes. The soap paste formed was thenremoved from the pressure vessel by means of a discharge pipe whichextended down to the bottom of the pressure vessel. The paste wasdissolved in 1500 cc. of water while stirring, and mixed with about 650cc. 20% sulfuric acid, thereby adjusting the pH value to 5 and resultingin the separation of a C fatty acid mixture at the surface. The mixturewas washed two times with hot water, whereafter about 300 grams of afinished product remained, which had the following characteristics:

Neutralization number 227 Saponification number 231 Pour point Cl. 7

The neutral oil distilled off had the following characteristics:

Saponification number 0.3

6 Example 2 600 grams of an intermediate fraction which had beenobtained in the distillation of a'C alcohol were charged to thepressure-resistant melting vessel used in Example 1. The alcohol hadbeen produced from chlorinated and dehydrochlorinated paraflins of themolecular size C by the catalytic addition of water gas and subsequenthydrogenation. The intermediate fraction had the followingcharacteristics:

Density at 20 C 0.804 Neutralization number 0.2 Saponification number1.4 Hydroxyl number 104 Iodine number 2 Carbonyl number 12 Refractiveindex, n 1.4402 Pour point C 6 This product was mixed with 50 grams NaOHand the mixture was further processed in accordance with Example 1. Thisresulted in 315 grams C hydrocarbons having the followingcharacteristics:

Density at 20 C 0.766 Refractive index, n 1.4285 Neutralization number 0Hydroxyl number 1 The treatment of the aqueous soap solution with acidresulted in about 290 grams of a C fatty acid mixture having thefollowing characteristics:

Neutralization number 224 Saponification number 231 Hydroxyl number 0Iodine number 0 Carbonyl number 0 Density at 20 C 0.883 Refractiveindex, n 1.4465 Pour point C -45 We claim:

1. Process for the treatment of an intermediate frac:

tion of alcohols and hydrocarbons obtained in the processing of higheralcohol mixtures produced from olefin mixtures in accordance with theoxo-synthesis which comprises contacting such an intermediate fractionwith an amount of caustic alkali at least substantially corresponding tothe hydroxyl number of the intermediate fraction contacting beingeffected at a temperature of about 250-350 C. and at an increasedpressure, distilling ofl? hydrocarbons from the melt formed by thealkali reaction, said distillation being at least partially effected ata reduced pressure, thereafter mixing an amount of water with the meltformed suflicient to form a pasty soap, decomposing the soap with amineral acid and recovering the fatty acid produced.

2. Process in accordance with claim 1, in which said contacting withcaustic alkali and mixing with water is effected in a pressure vessel,and in which after the formation of the pasty soap the same is removedfrom the pressure vessel at a temperature not in excess of about 200 C.

3. Process in accordance with claim 1, in which said contacting iseffected with an amount of caustic alkali not substantially in excess ofof the theoretically required quantity.

4. Process in accordance with claim 1, in which said contacting withcaustic, alkali is effected at a pressure of more than 10 kg. per squarecentimeter.

5. Process in accordance with claim 4, in which said contacting iseffected at about 50 kg. per square centimeter and the hydrogen splitoff during said contacting is continuously removed at apressure inexcess of 50 kg. per square centimeter.

6. Process in accordance with claim 1 in which, after the termination ofhydrogen evolution caused by said contacting with caustic alkali, thepressure is released to 5 atmospheric pressure.

7. Process in accordance with claim 1 in which said mixing with water isefiected with an amount of water of about 1050% of the melt treated.

References Cited in the file of this patent -UNITED STATES PATENTSStrosocker et a1 Sept; 12, 1933 Hennig May 23, 1939 Stephenson et a1Apr. 9, 1940 Chitwood Sept. 18, 1945 Hill Oct. 9, 1956 Bartlett et a1Aug. 6, 1957

1. PROCESS FOR THE TREATMENT OF AN INTERMEDIATE FRACTION OF ALCOHOLS ANDHYDROCARBONS OBTAINED IN THE PROCESSING OF HIGHER ALCOHOL MIXTURESPRODUCED FROM OLEFIN MIXTURES IN ACCORDANCE WITH THE OXO-SYNTHESIS WHICHCOMPRISES CONTACTING SUCH AN INTERMEDIATE FRACTION WITH AN AMOUNT OFCAUSTIC ALKALI AT LEAST SUBSTANTIALLY RESPONDING TO THE HYDROXYL NUMBEROF THE INTERMEDIATE FRACTION CONTACTING BEING EFFECTED AT A TEMPERATUREOF ABOUT 250-350*C. AND AT AN INCREASED PRESSURE, DISTILLING OFFHYDROCARBONS FROM THE MELT FORMED BY THE ALKALI REACTION, SAIDDISTRILLATION BEING AT LEAST PARTIALLY EFFECTED AT A REDUCED PRESSURE,THEREAFTER MIXING AN AMOUNT OF WATER WITH THE MELT FORMED SUFFICIENT TOFROM A PASTY SOAP, DECOMPOSING THE SOAP WITH A MINERAL ACID ANDRECOVERING THE FATTY ACID PRODUCED.